Its Alive!!!

[Cowman74]

I have been working on our 720D"s pony motor all winter. It hasn"t run it 20 years until tonight. It still has a issue with the carb. It only wants to run with the choke about 3/4 on. (thats why we quit using it) I had cleaned it good over the winter and it still does it. I need to play with the adjustments on the carb another evening but just excited i got it to run period. Anybody have any ideas on getting this thing running 100%? It has a brand new ignition box so i know thats good.

 

[Husker44A]

I would replace plugs and wires if you haven't done so already. 3/4 choke would be carb still plugged somewhere...

 

[Cowman74]

Its got new plugs and wires. Does anybody rebuild these little carbs?

 

[Husker44A]

I would think someones got to. If not have one on a shelf somewhere. Might google that carb. See what comes up. Whats the brand ?

 

[Cowguy74]

I wasn't able to find a make or model on it.

 

[Husker44A]

Post a message on here. Somebody got to know what brand of carb was used..

 

[BushogPapa]

Are expecting it to run unchoked before it warms up..?
I know that my 720D pony needs plenty choke for the first minute or two, before it settles down and idles..
I don't run mine as fast as the specs say and only open it up after I have engaged the pony, with the compression released on the big motor...

Ron..

 

[Pete in MD]

Cowman,

SM-2024 shows 720D starting engines using two different carbs:

Up to ser.7214898, Zenith TU3-1/2X1C
Ser. 7214899 and later, Zenith TU3X1C

The 70,80,730,820,& 830 used the same carbs.

Pete

 

[WeirdDeere]

First thing, I'd make sure you have a good flow of gas to the carb, if your rubber fuel line is old, it may be swelled up inside, restricting the flow. AND have a full tank of gas. Both my ponies need choke to even run if the tank is low.

These carbs are small, and have a couple little passages in them, which don't take much to clog.

If you take the little bowl off, most of the problems are found there. They are not hard to clean out, but take a little patience.

And if anything else, make sure you have a good float, and it's set to the right height.

Inside of the bowl:
<a href="http://s108.photobucket.com/albums/n8/weirddeere/?action=view&amp;current=100_9509.jpg" target="_blank">

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Get a screwdriver of the RIGHT size, and remove the little "compensator jet" out of the bottom of the bowl. Maybe use a bit of gentle heat if necessary. Remove the large main jet too (barely visible on the upper left)

Flip the carb over and remove the two bolts/plugs
<a href="http://s108.photobucket.com/albums/n8/weirddeere/?action=view&amp;current=100_9511.jpg" target="_blank">

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And remove the metering well. Use a proper screwdriver too, and take it easy.

<a href="http://s108.photobucket.com/albums/n8/weirddeere/?action=view&amp;current=100_9507.jpg" target="_blank">

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The part of the bowl that bolts to the rest of the carb.

Once you get all those parts out, you can use compressed air and carb cleaner to get 'er clean and running good again. Even use a thin wire in passages if necessary. I've pulled the bowl off before when it started running bad, cleaned it, and put 'er back on, and it cured everything.

ALSO, it would be a good idea to remove the idle jet from the carb body. It looks like a large flat headed screw with a long tube, and it pokes into the bowl. Take it out, and blow through it with air, make sure that it is clear as well.

Ideally you want the carb to look like this when you're working on it Heheh
<a href="http://s108.photobucket.com/albums/n8/weirddeere/?action=view&amp;current=100_9526.jpg" target="_blank">

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And this when done
<a href="http://s108.photobucket.com/albums/n8/weirddeere/?action=view&amp;current=OldSchoolFuel_3.jpg" target="_blank">

</a>

Brandon

 

[TJ in IN]

Burreycarb.com has does a fantastic job rebuilding my carburetors

 

[dennis oconnor]

In the bad old days, we would dunk the disassembled carb parts in a gallon kit of carb cleaner - the bad stuff that had a floating layer on top to keep it out of your lungs...
Today, I would make up a mix of 25% Muriatic Acid and 75% water (add the acid TO the water, slowly)and soak the parts in that... Check frequently to be sure nothing is being 'eaten' by the acid...

 

[WeirdDeere]

I've used acid on one of these carbs, but I don't think it did the bowl any good at ALL. It's aluminum. I'd be as careful as possible and avoid acid myself.

The body is cast iron, so it's tough.

Brandon